Highly porous Sr-doped TiO2 ceramics maintain compressive strength after grain boundary corrosion

Anne Klemm,Hanna Tiainen

doi:10.1016/j.jeurceramsoc.2021.04.059

Abstract

Maintaining sufficient mechanical support during bone healing is an essential property for ceramic bone scaffolds. However, grain boundary (GB) dissolution may compromise the mechanical strength of polycrystalline ceramics in the physiological environment. Therefore, we investigated the GB formation and its impact on the compressive strength and corrosion behavior in TiO2 scaffolds doped with calcium and strontium. To alter the GB composition and densification process, sintering conditions were altered. Prolonged sintering times and increased sintering temperature led to improved densification and increased strength in Ca-doped scaffolds. However, dissolution of the resulting amorphous GBs caused a significant loss of compressive strength when exposed to an acidic environment. In contrast, a crystalline SrTiO3 GB phase present in Sr-doped scaffolds, for which increased sintering temperature combined with rapid cooling led to a significantly improved compressive strength. Formation of SrTiO3 crystals in the GBs maintained the strength for over 4 weeks in an acidic environment.

Highlights

Ceramic titanium dioxide (TiO2) foams have excellent characteristics to be used in different applications such as catalysts in air and water purification systems, diesel particulate filters and as bone graft materials [1,2,3,4,5,6,7,8]
The present study focused on investigating the influence of amor phous and crystalline phases on grain boundary corrosion in highly porous TiO2 scaffolds doped with calcium and strontium
As shown in a previous study, the densification of the strut morphology observed in both Ca- and Sr-doped TiO2 scaffolds result in a significant increase in compressive strength of these scaffolds in comparison to the undoped control scaffolds [21]

Summary

Introduction

Ceramic titanium dioxide (TiO2) foams have excellent characteristics to be used in different applications such as catalysts in air and water purification systems, diesel particulate filters and as bone graft materials [1,2,3,4,5,6,7,8]. The highly interconnected pore structure of TiO2 foam enables vascularisa tion and osteogenesis within the entire scaffold volume [6,10]. Despite their high interconnected porosity, TiO2 foams have compressive strength that is comparable to human trabecular bone, making TiO2 scaffolds suitable for bone tissue engineering applications [5]. During the inflammatory phase of the bone remodeling process, macrophages and osteoclasts acidify the microenvironment at the bone defect site [13,14] This aggressive chemical environment can cause dissolution of poorly crystalline ceramic grain boundaries, and result in a significant loss in compressive strength [11,15,16]. Other techniques need to be investigated to protect the grain boundaries from the external environment and prevent corrosion

Methods

Results

Conclusion